EPROM compatibility question

[JLukas]

A general question on 27C010-27C080 32-pin EPROMs (1-8 megabit) - how important is it for the EPROM to match the size the board was designed for?

For example, if a socket originally accepted a 27C040 4 megabit EPROM, could I put in a 27C020 2 megabit EPROM in (or even a 27C010 1 megabit EPROM), assuming that's all the capacity I need?

Another example, how about an 8 megabit chip instead of 4 megabit? From what I found searching, the PCB would only see 4 megabit of it unless it has support using a jumper change.

With this range of EPROMS, is the pinout close enough where it can at least be safely tested, or is there a risk of frying the chip and/or board?

[DogP]

For reading, the chips are pretty much compatible. For programming, you'd need to make sure you select the correct chip since the program enable and programming voltage pins vary between models. Also, if going up in size (for example 27C080 in a 27C010 socket), you need to make sure the extra address lines are connected to either +5 or GND (or use switches/extra address lines if you're wanting to use the full size of the ROM) since the extra pins may or may not be connected at all, or to the voltage you want to address your data.

It's easy enough to find the pinouts for all the chips though, so just look them up and everything should be pretty obvious.

DogP